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    <title>把括号内的URL用content属性插入到每个链接后面</title>
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        a:after {
            content: " (" attr(href) ")";
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    <p><a href="http://www.runoob.com">菜鸟教程</a> - 免费的编程学习网站。</p>
    <p><a href="http://www.runoob.com">Google</a> - 好用的搜索引擎。</p>
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